This invention relates to the preparation of iridium-containing films on substrates, particularly on semiconductor device structures.
Films of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. For example, high quality RuO2 thin films deposited on silicon wafers have recently gained interest for use in ferroelectric memories. Many of the Group VIII metal films are generally unreactive toward silicon and metal oxides, resistant to diffusion of oxygen and silicon, and are good conductors. Oxides of certain of these metals also possess these properties, although perhaps to a different extent.
Thus, films of Group VIII metals and metal oxides, particularly the second and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt) have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for electrical contacts. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices, such as ferroelectric memories. Furthermore, they may even be suitable as the plate (i.e., electrode) itself in capacitors. Iridium oxide is of particular interest as a barrier layer because it is very conductive (30-60 xcexcxcexa9-cm) and is inherently a good oxidation barrier.
Capacitors are the basic charge storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs). It is important for device integrity that oxygen and/or silicon not diffuse into or out of the dielectric material. This is particularly true for ferroelectric RAMs because the stoichiometry and purity of the ferroelectric material greatly affect charge storage and fatigue properties.
Thus, there is a continuing need for methods and materials for the deposition of metal-containing films, such as iridium-containing films, which can funcation as barrier layers, for example, in integrated circuits, particularly in random access memory devices.
The present invention is directed to methods for manufacturing a semiconductor device, particularly a ferroelectric device. The methods involve forming iridium-containing films on substrates, such as semiconductor substrates or substrate assemblies during the manufacture of semiconductor structures. The iridium-containing film can be a pure iridium film, an iridium oxide film, an iridium silicide film, an iridium sulfide film, an iridium selenide film, an iridium nitride film, or the like. Typically and preferably, the iridium-containing film is electrically conductive. The resultant film can be used as a barrier layer or electrode in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device.
The metal-containing film can include pure iridium, or an iridium alloy containing iridium and one or more other metals (including transition metals, main group metals, lanthanides) or metalloids from other groups in the Periodic Chart, such as Sixe2x80x94, Ge, Sn, Pb, Bi, etc. Furthermore, for certain preferred embodiments, the metal-containing film can be an oxide, nitride, sulfide, selenide, silicide, or combinations thereof.
Thus, in the context of the present invention, the term xe2x80x9cmetal-containing filmxe2x80x9d includes, for example, relatively pure films of iridium, alloys of iridium with other Group VIII transition metals such as rhodium, nickel, palladium, platinum, iron, ruthenium, and osmium, metals other than those in Group VIII, metalloids (e.g., Si), or mixtures thereof. The term also includes complexes of iridium or iridium alloys with other elements (e.g., O, N, and S). The terms xe2x80x9csingle transition metal filmxe2x80x9d or xe2x80x9csingle metal filmxe2x80x9d refer to relatively pure films of iridium. The terms xe2x80x9ctransition metal alloy filmxe2x80x9d or xe2x80x9cmetal alloy filmxe2x80x9d refer to films of iridium in alloys with other metals or metalloids, for example.
One preferred method of the present invention involves forming a film on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure. The method includes: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a precursor composition comprising one or more complexes of the formula:
LyIrYz,
wherein: each L group is independently a neutral or anionic ligand; each Y group is independently a pi bonding ligand selected from the group of CO, NO, CN, CS, N2, PX3, PR3, P(OR)3, AsX3, AsR3, As(OR)3, SbX3, SbR3, Sb(OR)3, NRHxR3xe2x88x92x, CNR, and RCN, wherein R is an organic group and X is a halide; y=1 to 4; z=1 to 4; x=0 to 3; and forming a metal-containing film from the precursor composition on a surface of the substrate (preferably, the semiconductor substrate or substrate assembly). In certain embodiments, the process is carried out in a nonhydrogen atmosphere (i.e., an atmosphere that does not include H2). In other embodiments, L is not a cyclopentadienyl ligand when Y is a CO ligand. The metal-containing film can be a single transition metal film or a transition metal alloy film, for example. Using such methods, the complexes of Formula I are converted in some manner (e.g., decomposed thermally) and deposited on a surface to form a metal-containing film. Thus, the film is not simply a film of the complex of Formula I.
Complexes of Formula I are neutral complexes and may be liquids or solids at room temperature. Typically, however, they are liquids. If they are solids, they are preferably sufficiently soluble in an organic solvent or have melting points below their decomposition temperatures such that they can be used in flash vaporization, bubbling, microdroplet formation techniques, etc. However, they may also be sufficiently volatile that they can be vaporized or sublimed from the solid state using known chemical vapor deposition techniques. Thus, the precursor compositions of the present invention can be in solid or liquid form. As used herein, xe2x80x9cliquidxe2x80x9d refers to a solution or a neat liquid (a liquid at room temperature or a solid at room temperature that melts at an elevated temperature). As used herein, a xe2x80x9csolutionxe2x80x9d does not require complete solubility of the solid; rather, the solution may have some undissolved material, preferably, however, there is a sufficient amount of the material that can be carried by the organic solvent into the vapor phase for chemical vapor deposition processing.
Yet another method of forming a metal-containing film on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure, involves: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a precursor composition comprising one or more organic solvents and one or more precursor complexes of Formula I as defined above; vaporizing the precursor composition to form vaporized precursor composition; and directing the vaporized precursor composition toward the substrate to form a metal-containing film on a surface of the substrate. In certain embodiments, the process is carried out in a nonhydrogen-containing atmosphere. In other embodiments, L is not a cyclopentadienyl ligand when Y is a CO ligand. Herein, vaporized precursor composition includes vaporized molecules of precursor complexes of Formula I either alone or optionally with vaporized molecules of other compounds in the precursor composition, including solvent molecules, if used.
Preferred embodiments of the methods of the present invention involve the use of one or more chemical vapor deposition techniques, although this is not necessarily required. That is, for certain embodiments, sputtering, spin-on coating, etc., can be used.
Methods of the present invention are particularly well suited for forming films on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. It is to be understood that methods of the present invention are not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, the methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies can be used in methods of the present invention. These include, for example, fibers, wires, etc. If the substrate is a semiconductor substrate or substrate assembly, the films can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers to the semiconductor substrate having one or more layers or structures formed thereon.
A chemical vapor deposition apparatus is also provided. The apparatus includes a deposition chamber having a substrate positioned therein; a vessel containing a precursor composition comprising one or more complexes of Formula I as described above; and a source of an inert carrier gas for transferring the precursor composition to the chemical vapor deposition chamber.